<template>
  <div class="pagination">
    <button :disabled="pageNo === 1">上一页</button>
    <button v-show="startEndPage.start > 1" :class="{ active: pageNo === 1 }" @click="$emit('changePage',1)">
      1
    </button>

    <button v-show="startEndPage.start > 2">···</button>

    <button
      v-for="page in startEndArr"
      :key="page"
      :class="{ active: pageNo === page }"
      @click="$emit('changePage',page)"
    >
      {{ page }}
    </button>

    <button v-show="startEndPage.end <= totalPages - 1">···</button>
    <button
      v-show="startEndPage.end < totalPages"
      :class="{ active: pageNo === totalPages }"
      @click="$emit('changePage',totalPages)"
    >
      {{ totalPages }}
    </button>
    <button :disabled="pageNo === totalPages">下一页</button>

    <button style="margin-left: 30px">共{{ totalPages }}页</button>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  props: ["totalPages", "pageNo", "continuPage"],
  computed: {
    startEndPage() {
      let start = 0,
        end = 0;
      if (this.totalPages < this.continuPage) {
        start = 1;
        end = this.totalPages;
      } else {
        start = this.pageNo - Math.floor(this.continuPage / 2);
        end = this.pageNo + Math.floor(this.continuPage / 2);
        if (start < 1) {
          (start = 1), (end = this.continuPage);
        }
        if (end > this.totalPages) {
          start = this.totalPages - this.continuPage + 1;
          end = this.totalPages;
        }
      }
      return { start, end };
    },
    startEndArr() {
      const arr = [];
      for (let i = 1; i <= this.startEndPage.end; i++) {
        if (i >= this.startEndPage.start) {
          arr.push(i);
        }
      }
      return arr;
    },
  },
};
</script>

<style lang="less" scoped>
.pagination {
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
</style>
